These are still a common tool today, although these older craftsman's seem to be a little over-sized and not as supportive, the idea is the steel spring prevents the copper or aluminum tubing from collapsing when bending it especially tight bends. These is also internal version which I think work a little better and you can use both external and internal at the same time for extra support.
Craftsman #9-55411
23 авг 2024
